Numerical and Experimental Thermal Analysis of a Tunnel Kiln used in Ceramic Production

The available technology for tunnel kilns in Brazil is practically empirical and there is a lack of fundamental studies developed as an aid for the design of new kilns or for the retrofit of old ones. Here, a thermal model of a tunnel kiln is developed allowing the numerical simulation of kilns and dryers aiming toward a more efficient and less energy consuming design. The model is then systematically applied in the design of a new kiln to be used for firing clay tiles, bricks and similar products, with natural gas and sawdust as fuels. The results include the three-dimensional temperature distribution within the walls, gas and load along the kiln and a complete thermal energy balance including all energy fluxes related to the process. The strategies for kiln design are discussed and the advantages of combining the low cost of the wood sawdust and the ease of adjustment and quality of the natural gas combustion are evidenced.